The present invention relates to the stepwise bending of metal strip or skelp into a split tube or pipe to be fed subsequently through a welding machine.
U.S. Pat. No. 3,472,053 discloses a tube mill, having a plurality of stands for bending strip stepwise into a split tube or pipe. Each stand receives a partially bend strip of trough-shaped contour and establishes a new, intermediate contour of particular arch length and increased curvature. Each stand is adjustable as to these working parameters so that the same mill can process differently wide strips in order to obtain tubes of different diameters. It is required to change and adjust each stand if differently wide skelp is to be processed, this being quite a cumbersome procedure. Moreover, these stands are rather heavy and large because they include more or less complicated adjusting mechanisms, and the bending rolls are variably mounted pursuant to their adjustment features.